Hydraulic press

ABSTRACT

A hydraulic press having a fluid chamber and a piston slidably mounted therein so as to separate said chamber into a pair of portions. A conduit of &#39;&#39;&#39;&#39;excessive&#39;&#39;&#39;&#39; length connects the chamber portions and functions as a valve in point of time to provide the desired isolation of the chamber portions from each other and also to provide intensified pressure on the desired side of the piston.

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s4] HYD 1 AIUMC PRESS FOREIGN PATENTS OR APPLECATZONS [72] Inventor:Peter B. Olmsted, Ann Arbor, Mich. 308,648 11/1969 Sweden ..100/269 IR[73] Asslgnee: Olmsted Products (30., Ann Arbor, MlCh. Pfimary Examinerwalter A scheel [22] Filed: Dec. 6, 1969 Assistant Examiner-Alan I.Cantor [21] pp No 882 222 Attorney-Olsen and Stephenson AEfiTRACT (g1. Ahydraulic press having a fluid chamber and a piston Slidably I 58] Fieid/1 6 mounted therein so as to separate said chamber into a pair of"25/84 83/639 portions. A conduit of excessive length connects thechamber portions and functions as a valve in point of time to providethe desired isolation of the chamber portions from [56] References cuedeach other and also to provide intensified pressure on the UNITED STATESPATENTS desired side of the piston. 3,168,033 2/1965 Hansen /269 R X 3Claims, 5 Drawing ifiigu PATENTEU JAN 1' 8 m2 FIG] INVENTOR PETER B.OLMSTED ATTORNEYS This invention relates generally to presses and moreparticularly to a hydraulic press capable of high-speed operation andeconomical manufacture. The press of this invention includes a pair ofhydraulic chambers arranged in tandem. A piston slidably mounted in oneof the chambers has a plunger secured to one of its sides and theplunger supports the usual movable press platen. A body on the oppositeside of the piston projects into the second fluid chamber. A source offluid communicates through a supply line with the first chamber on thebody member side of the piston. A control valve is connected to thefirst chamber on both sides of the piston, to the second chamber, and totank.

The most important feature of the press of this invention is theinclusion therein of a conduit of excessive" length, sometimes referredto herein as a "long line or a transfer line, connected to the firstchamber on both sides of the piston. During the approach of the pistonto the working portion of its stroke, the transfer line is operative totransfer fluid for regenerative action from the plunger side of thepiston to the body member side of the piston to provide for high-speedmovement of the piston with a relatively small size power supply. Duringthe working portion of the stroke, the transfer line, by virtue of itslength, provides the desired isolation of the chamber portions onopposite sides of the piston for a period of time so that the rapidlymoving fluid in the transfer line imparts its momentum force tointensify fluid pressure in the body member side of the piston. Thetransfer line also acts to evacuate the plunger side of the chamberduring the working portion of the stroke so as to increase the workingstroke power of the press.

The principal object of this invention, therefore, is to provide animproved high-speed press which can be manufactured at a low cost.

Further objects, features and advantages of this invention will becomeapparent from a consideration of the following description, the appendedclaims, and the accompanying drawing in which:

FIG. 1 is an elevational view of the press of this invention, with somepartsbroken away and other parts shown in section for the purpose ofclarity;

FIGS. 2, 3 and 4 are diagrammatic views of the control valve in thepress of this invention, showing the control valve in progressivelymoved stop," power and return positions; and

FIG. 5 is a graph illustrating a cycle of operation of the press of thisinvention through a working stroke.

With reference to the drawing, the press of this invention indicatedgenerally at 10, is illustrated in FIG. l as including a housing 12supported on a stationary frame M which carries the stationary platen 16for the press 110. A movable platen Ml is secured to a plunger 20 whichextends into a first fluid chamber 22 formed in the housing l2. A piston24, slidably supported in the chamber 22, has the plunger 20 arranged sothat it projects from one side of the piston 2d. A body 28, of largercross-sectional size than the plunger 20 projects from the opposite sideof the piston 24 into a second fluid chamber 32 formed in the housingl2.

A control valve, indicated generally at 34 in FIG. l, is connected by aline 36 to the chamber 22 on the side 30 of the piston 24. The valve 3 1is also connected by a conduit 3% to the chamber 22 on the opposite sideof the piston 24. A conduit 40 connects the valve 34 to a tank orreservoir 42 and a conduit 44! connects the control valve 341 to thechamber 32. An elongated supply line 46 connects the chamber 22, on theside 30 of the piston 24, to a source of fluid under pressure,illustrated as an accumulator 48 connected through a check valve 50 to apump 52 which also communicates with the reservoir 42.

in the operation of the press 110. assume that both fluid chambers arefull of fluid and that the control valve 34 is in its "stop positionillustrated in FlG. 2. in this position of the control valve 3d, itoperates to communicate the conduits 3n and 38 with each other and blockthe conduits ilt) and 44. As a result, the fluid pressures on oppositesides of the piston 24 are equal, which results in a higher force on theside 26 of the piston M by virtue oi the increased area on the side 26.However, the piston 24 will not move because tiuid is locked in thechamber 32.

Now assume that the control valve Ed is moved to its power" positionshown in Fit 3. in this position of the control valve, it provides forcommunication of the conduits 3b and 44 and it blocks the conduits Elliand ill. As a result, the fluid pressure in the chamber 22 on the side30 of the piston 24 is increased relative to the pressure on the side26, and fluid is pumped into both the chambers and 32. The piston 24 isthus rapidly forced downwardly to accelerate the platen ill in adownward direction until the work, illustrated at 5 3 between theplatens l6 and lltl, is contacted so that it exerts an upward load onthe platen lb. During this accelerating downward movement of the piston24, fluid in the chamber 22 on the side 26 of the piston 24 is forcedout of the chamber 22 through a conduit 56 which connects to the chamber22 on the opposite side 30 of the piston 24.

The conduit as is unrestricted and is of excessive" length, by which ismeant it is significantly greater than that required to connect theportions 220 and 22b of chamber 22 on opposite sides of the piston Morespecifically, as used herein, the term excessive length shall mean atleast twice as long as necessary to connect the chamber portions 22a and22b. As the piston 24 proceeds in a downward direction the pressure inchamber portion 22a will at some point in time be higher than thepressure in chamber portion 221; but this will not slow down the piston24 because of the momentum of the piston 24 at such time. The long line56 is of suii'icient length to effectively isolate the chamber portions22a and 22!) so that the pressures therein are not equalized when thepressure in portion 22b later exceeds the pressure in chamber portion22a by a substantial amount.

When the piston 24 slows down due to the platen l8 contacting the work5d, the momentum of fluid in long line 56 continues to provide forremoval of oil from chamber portion 22a and deliver it to chamberportion 22b thus intensifying the pressure in chamber portion 22b andchamber 32 when such higher pressure is most useful. As a result, someevacuation of portion 22a takes place and the working pressuresdeveloped in chambers 22b and exceed the pressure available from source42%. The transfer line 5h acts as a valve to isolate the chamber 22 onopposite sides of the piston 24 from each other for a period of timeapproximately equal to the time required for a pressure wave to travelthe length of the transfer line 56. For this reason, the long line 56 isof a length equal to TXC where T equals the length of time in secondsthat a near rated working force is required at the platen lid to performthe desired work with the press l0, and (3 equals the velocity of soundin the working fluid measured in inches per second. in most cases thefluid used in the press i0 is a high density phosphate ester based fluidin which the velocity of sound is 50,000 inches per second.

Thus, by forming the transfer line 5d of this length, it acts toevacuate the chamber 22 when acceleration of the piston 2.4 is desiredand to intensify the pressure on the piston 2 5 during the time that thework is being completed and the highest pressure is required. This iswhy the line 5'6 is of a length approximately equal to the lengthrequired for a pressure wave to travel the length of the pipe during thetime work is being performed. Thus, in the case where a near ratedworking force is required for 0.006 second, die sound in the workingfluid is 50,000 inches per second, a 300 inch transfer line 561 isrequired. Since the pressure in chamber portion 22 will at times exceedthe pressure available at source 40, the supply line do should be atleast half the length of long line 56 in order to avoid dissipating thisincreased pressure, which will occur when a pressure wave has travelledfrom chamber 22b through line db to source and back again.

When the work has been completed and it is desired to raise the platenill, the control valve is moved to the return position illustrated inFIG. 4. In this position of the control valve 34, the conduits 40 and-44are connected and the conduits 36 and 38 are connected. As a result ofthe connection of the conduits 36 and 38, the fluid pressure on thelarger area side 26 of the piston 24 is the same as the fluid pressureon the side 30. The result is a larger force on the side 26 than on theside 30 thereby causing the piston 24 to move upwardly and move the body28 into the chamber 32 so as to force fluid therein to flow through theconduit 44 and the conduit 40 to the tank 42. The above cycle can thenbe repeated.

From the above description it is seen that this invention provides ahydraulic press 10 in which the piston 24 can be selectively held in oneposition, moved downwardly during the power stroke, or moved upwardly inthe return stroke by manipulation of the control valve 34. By virtue ofthe cooperative relationship of the'chambers 22 and 32 and the long line56, the piston 24 is rapidly movable and the desired regenerative actionis obtained on the power stroke. This action is illustrated in FIG. inwhich the pressure in the chamber portion 22b on the side 30 of thepiston 24 is plotted against time commencing with initial downwardmovement of platen 18. Prior to contact of the platen 18 with the workthe pressure is relatively constant and is indicated at 60. As theplaten 18 moves into the work the pressure rises along the line 62, thedips 64 in the line 62 being caused by movement of piston 24 faster thanthe supply of fluid to chamber portion 22b. Finally the pressure 66necessary to achieve the desired near rated working force is reached andthis pressure 66 remains nearly constant until it drops to zero at theend of the cycle. The length of the line showing pressure 66 is T in theabove equation.

What is claimed is:

1. In a press having a fixed platen and a movable platen, means forminga fluid chamber, a piston slidably mounted in said chamber so that afirst portion of said chamber is located on one side of said piston andanother portion of said chamber is on the opposite side of said piston,a plunger on one side of said piston connected to said movable platen,means connected to said chamber for supplying fluid thereto on theopposite side of said piston, and unrestricted conduit means ofexcessive length extending between and connecting said chamber portions.

2. The structure according to claim 1 wherein said means for supplyingfluid to said chamber comprises a source of fluid under pressure and aline connecting said source and said chamber, said line being of alength approximately equal to one half the length of said conduit means.

3. In a press having the structure set forth in claim 1 furtherincluding body means extending from the opposite side of said piston,said body means and said plunger being of relative sizes such that thearea of said one side of said piston exposed to fluid in said chamber isgreater than the area of said opposite side exposed to fluid in saidchamber, means forming a second fluid chamber separate from said firstchamber and located so that said body means projects into said secondchamber, and control valve means connected to said first fluid chamberon both sides of said piston and connected to said second fluid chamberand to a tank.

1. In a press having a fixed platen and a movable platen, means forminga fluid chamber, a piston slidably mounted in said chamber so that afirst portion of said chamber is located on one side of said piston andanother portion of said chamber is on the opposite side of said piston,a plunger on one side of said piston connected to said movable platen,means connected to said chamber for supplying fluid thereto on theopposite side of said piston, and unrestricted conduit means of''''excessive'''' length extending between and connecting said chamberportions.
 2. The structure according to claim 1 wherein said means forsupplying fluid to said Chamber comprises a source of fluid underpressure and a line connecting said source and said chamber, said linebeing of a length approximately equal to one half the length of saidconduit means.
 3. In a press having the structure set forth in claim 1further including body means extending from the opposite side of saidpiston, said body means and said plunger being of relative sizes suchthat the area of said one side of said piston exposed to fluid in saidchamber is greater than the area of said opposite side exposed to fluidin said chamber, means forming a second fluid chamber separate from saidfirst chamber and located so that said body means projects into saidsecond chamber, and control valve means connected to said first fluidchamber on both sides of said piston and connected to said second fluidchamber and to a tank.